Fluid flow shutoff valve

ABSTRACT

A fluid system (10) has a shutoff valve (13) positioned between a fluid tank (11) and the intake side of a pump (12). The valve (13) includes a valve spool (21) movable between a first position at which an inlet port (18) connected to the fluid tank (11) is blocked from communication with an outlet port (19) connected to an intake side of the pump (12) and a second position at which the inlet port (18) is in communication with the outlet port (19). A passage (26) connects the outlet port (19) to a first chamber (23) at one end of the valve spool (21) while a port (27) connects the discharge side of the pump (12) to a second chamber (24) at the opposite end of the valve spool (21). A spring (29) resiliently urges the valve spool (21) to the first position.

TECHNICAL FIELD

This invention relates to a shutoff valve which automatically blocksfluid flow from a fluid tank in response to the absence of any demandfor fluid from the tank.

BACKGROUND ART

Many earthmoving vehicles have the fuel tank positioned higher than theengine. Thus, should a rupture or break occur in the fuel line orcomponent of the fuel system, the fuel would be gravity fed through suchrupture. In some such vehicles a solenoid valve is positioned within thefuel line and is activated in response to an electrical signal directedthereto. However, deactivating the solenoid valve to a shutoff positionhas heretofore been done manually and would not necessarily occurautomatically. Further, a solenoid valve of a size sufficient to handlethe fuel flow without restricting the fuel flow is rather costly andgreatly increases the overall cost of the fuel system.

SUMMARY OF INVENTION

In one aspect of the present invention, a fuel flow shutoff valve isprovided which shifts to an open position in response to a demand forfluid from the tank and automatically shifts to a closed position inresponse to the absence of a positive demand for fluid from the tank.Specifically, the fluid flow shutoff valve includes a valve spoolslidably positioned within a bore of a body and movable between a firstposition at which an inlet port is blocked from communication with anoutlet port and a second position at which the inlet port is incommunication with the outlet port. A passage connects the outlet portto a first chamber positioned at one end of the spool while a pressureport is connected to a second chamber at the opposite end of the valvespool. A spring resiliently urges the valve spool to the first positionand has sufficient resiliency to be overcome by the force exerted on thevalve spool in response to a partial vacuum being created in the firstchamber.

BRIEF DISCRIPTION OF THE DRAWING

The sole FIGURE is a diagrammatic sectional view of an embodiment of thepresent invention depicted in a fluid system.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawing a fluid system is generally indicated by thereference numeral 10 and includes a fluid tank 11, a pump 12 connectedto draw fluid from the tank 11, a fluid flow shutoff valve 13 positionedbetween the fluid tank 11 and the intake of pump 12, and a work system14 connected to the discharge side of pump 12. In one example the worksystem 14 can be a fuel system for delivering fuel to an engine andfluid tank 11 can be a fuel tank for supplying fuel to the fuel system.

The fuel flow shutoff valve 13 includes a body 16 having a bore 17 andan inlet port 18 and an outlet port 19 communicating with the bore. Theinlet port 18 is connected to fluid tank 11 and outlet port 19 isconnected to the intake side of pump 12.

A valve spool 21 is slidably positioned within bore 17 and has anannular groove 22 provided thereon. Valve spool 21 is movable between afirst position at which inlet port 18 is blocked from communication withoutlet port 19 by valve spool 21 and a second position at which inletport 18 is in communication with outlet port 19 via annular groove 22.

First and second chambers 23,24 are provided in bore 17 at opposite endsof valve spool 21. A passage 26 connects outlet port 19 to first chamber23. A pressure port 27 is connected to second chamber 24 and to a pilotline 28 connected to the discharge or pressure side of pump 12 betweenpump 12 and work system 14.

A means, for example, a compression spring 29 positioned within firstchamber 23 is provided for resiliently urging valve spool 21 to thefirst position. Compression spring 29 has sufficient resiliency to beovercome by the force exerted on valve spool 21 in response to a partialvacuum of a preselected value being created in first chamber 23 by pump12.

INDUSTRIAL APPLICABILITY

In use when pump 12 is not being driven, valve spool 21 will beresiliently urged to the first position as shown in the drawing byspring 29. Upon starting the pump 12, since the pump is initiallyblocked from drawing fluid from fluid tank 11 by valve spool 21, apartial vacuum is created in outlet port 19, passage 26, and firstchamber 23. The partial vacuum in first chamber 23 causes a force to beexerted on valve spool 21 and when the vacuum reaches a preselectedvalue the force acting on the valve spool overcomes the resiliency ofspring 29 causing valve spool 21 to be moved to the second position. Atthe second position of valve spool 21, fluid is drawn from fluid tank 11by pump 12 and directed to work system 14. The pressurized fluid is alsodelivered through pilot line 28, pressure port 27 and into secondchamber 24 where it then holds valve spool 21 at the second position aslong as pump 12 is driven. When pump 12 is stopped, such that there isno positive demand for fluid by the pump and hence no pressurized fluidbeing delivered to chamber 24, spring 29 will automatically return valvespool 21 to the first position again blocking fluid flow from fluid tank11.

Thus, from the foregoing it is readily apparent that the shutoff valvewill operate automatically to stop fluid flow from fluid tank 11 inresponse to an absence of a positive demand for fluid from the tank.Moreover, the shutoff valve is of simple construction and can bemanufactured in convenient sizes economically.

What is claimed is:
 1. A fluid flow shutoff valve (13) for positioningwithin a fluid system (10) having a fluid tank (11) and a pump (12),comprising:a body (16) having a bore (17) and an inlet port (18) and anoutlet port (19) in communication with said bore (17); a valve spool(21) slidably positioned within the bore (17) and movable between afirst position at which the inlet port (18) is blocked fromcommunication with the outlet port (19) and a second position at whichthe inlet port (18) is in communication with outlet port (19); saidvalve spool (21) and said body (16) defining first and second chambers(23,24) at opposite ends of said valve spool; a passage (26) connectingthe outlet port (19) to the first chamber (23); a pressure port (27)connected to the second chamber (24); a spring (29) positioned withinthe first chamber (23) and resiliently urging the valve spool (21) tothe first position, said spring (29) having sufficient resiliency to beovercome by the force exerted on the valve spool (21) in response to apartial vacuum being created in said first chamber (23); and whereinsaid inlet port (18) is connected to said fluid tank (11) and saidoutlet port (19) is connected to the pump (12) and including means (28)for directing pressurized fluid from the pump (12) to the pressure port(27) and hence into second chamber (24).
 2. A fluid system (10)comprising:a fluid tank (11); a work system (14); a fluid pump (12)having an intake side connected to said fluid tank (11) and itsdischarge side connected to said work system (14); a shutoff valve (13)positioned between said fluid tank (11) and said fluid pump (12), saidshutoff valve (13) including a body (16) having a bore (17), an inletport (18) connecting the bore (17) to said fluid tank (11), an outletport (19) connecting the bore (17) to the intake side of said pump (12),a valve spool (21) slidably positioned within the bore (17) and movablebetween a first position at which the inlet port (18) is blocked fromcommunication with the outlet port (19) and a second position at whichthe inlet port (18) is in communication with the outlet port (19), aspring (29) connected to said valve spool and resiliently urging thevalve spool to the first position, first and second chambers (23,24)positioned at opposite ends of the valve spool (21), a passage (26)connecting the outlet port (19) to the first chamber (23), and apressure port (27) connected to the second chamber; and means (28) forconnecting the discharge side of said pump (12) to said pressure port(27).